blockWetBulb_TDryBulPhi

Block to compute the wet bulb temperature based on relative humidity
Diagram of WetBulb_TDryBulPhiOpen the diagram
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Information

This block computes the wet bulb temperature for a given dry bulb temperature, relative air humidity and atmospheric pressure.

The block uses the approximation of Stull (2011) to compute the wet bulb temperature without requiring a nonlinear equation. The approximation by Stull is valid for a relative humidity of 5% to 99%, a temperature range from -20°C to 50°C and standard sea level pressure. For this range of data, the approximation error is -1 Kelvin to +0.65 Kelvin, with a mean error of less than 0.3 Kelvin.

The model is validated in Buildings.Controls.OBC.CDL.Psychrometrics.Validation.WetBulb_TDryBulPhi.

References

Stull, Roland. Wet-Bulb Temperature from Relative Humidity and Air Temperature Roland Stull. Journal of Applied Meteorology and Climatology. Volume 50, Issue 11, pp. 2267-2269. November 2011 DOI: 10.1175/JAMC-D-11-0143.1

Connectors

TypeNameDefaultDescription
Buildings.Controls.OBC.CDL.Interfaces.RealInputTDryBulDry bulb temperature
Buildings.Controls.OBC.CDL.Interfaces.RealInputphiRelative air humidity
Buildings.Controls.OBC.CDL.Interfaces.RealOutputTWetBulWet bulb temperature

Revisions

  • March 6, 2023, by Michael Wetter:
    Added a constant in order for unit check to pass.
    See Buildings, issue 1711 for a discussion.
  • November 12, 2020, by Michael Wetter:
    Reformulated to remove dependency to Modelica.Units.SI.
    This is for Buildings, issue 2243.
  • September 29, 2020, by Michael Wetter:
    Removed unused input p and renamed block.
    This is for Buildings, issue 2139
  • April 11, 2017, by Jianjun Hu:
    Changed the model to avoid using nonlinear equation.
  • November 3, 2016, by Michael Wetter:
    Changed icon.
  • May 24, 2016, by Filip Jorissen:
    Corrected exact implementation. See Buildings, issue 474 for a discussion.
  • October 3, 2014, by Michael Wetter:
    Changed assignment of nominal value to avoid in OpenModelica the warning alias set with different nominal values.
  • November 20, 2013 by Michael Wetter:
    Updated model to use Buildings.Utilities.Psychrometrics.Functions.saturationPressure() and Buildings.Utilities.Psychrometrics.Functions.saturationPressureLiquid() as these functions have been moved from the medium to the psychrometrics package.
  • October 1, 2012 by Michael Wetter:
    First implementation.